Ram jet fuel metering unit



P 1951 w. K. DEACON 2,566,319

RAM JET FUEL METERING UNIT Filed April 12, 1946 I /5 I la I, I l/\ I 3mm I 46 WALTER k. beAcou Patented Sept. 4, i951 am JET FUEL METERING Um'r Walter K. Deacon, United States Navy Application April 12, 1946, Serial No. 661,636

12 Claims.

(Granted under the actof amended April 30, 1928;

The present invention relates to engines of the ram jet type and in particular to improvements in fuel systems therefor.

Prior to my invention it has been common practice to introduce liquid fuel into a ram jet combustion chamber by means of one or more nozzles which are fixed relative to the unit and supplied by a pressure source such as a motor driven pump or bottles having as therein under pressure. These systems have certain inherent disadvantages. First, stationary nozzles do not provide optimum atomization, vaporization, or mixing of fuel and air when introduced in a streamline air flow. Secondly, they require complicated metering devices to regulate the quantity of fuel flow under variable flight conditions and thirdly the added weight and complexity of the pressure source detracts from the overall efficiency of the unit.

The present invention overcomes the disadvantages aforementioned and has therefore as one of its objects the provision of a fuel system which utilizes available air as the power source to pump fuel to a combustion chamber.

Another object is the elimination of cumbersome energy sources such as batteries, bottles of compressed gas, etc., for pumping fuel used prior to this invention, thus decreasing the overall weight and complexity of the jet unit and hence increasing certain of its overall efficiencies.

Another object is the provision of a fuel systern which delivers the optimum amount of fuel to a combustion chamber without the use of complicated metering devices.

Another object is the provision of a fuel system which creates a turbulence in an otherwise streamline flow of air, introduces the fuel in this turbulent flow thus improving the combustion characteristics of the fuel-air mixture.

Further objects, advantages, and salient features of this invention will become apparent from a consideration of the description to follow, the accompanying drawing and the appended claims.

Fk. 1 represents a partly sectioned side elevational view of the broken away forward portion ofa ramietengine.

Fig. 2 enlarged side elevational view of a portion of Fig. 1, certain parts being shown in section Fig. 3 represents a modification of a control which may be used in the device of Fig. 2 or Fig.4.

Fig. 4 represents another modification of a portion of Fig.2.

Pig. 5 represents certain modifications of Fig. 1. I in March 3, 1883, a 370 O. G. 757) Referring to the drawing, in which corresponding parts are designated by like reference characters, Hi represents the forward portion of a ram jet engine casing which is divided into a mouth ll, diffuser section I! and combustion chamber (3. The cross sectional shape of the engine casing may be of various configurations but as illustrated all sections are circular.

A flame holder H which serves to maintain combustion may be provided in the region between the diifuser section and combustion chamber. When the ram jet is in motion air enters mouth II, has fuel added thereto as will hereinafter be more fully explained and the combustible mixture passes rearwardly to the combustion chamber I! where combustion takes place. The products of combustion then issue from a suitable nozzle (not shown) to provide thrust for the unit; The unit may be installed in a guided missile, other aircraft, or vehicle which employs a ram jet engine.

The fuel requirements of a ram Jet engine vary Substantially in direct proportion to mass air flow through the combustion chamber or otherwise stated, the fuel air mass ratio should remain substantially constant under variable flight conditions. The mass air flow under variable flight conditions is a function of forward velocity of the ram jet and ambient air density, the latter being a function of altitude. It follows therefore that if a pump can be made to deliver fuel at a rate directly proportional to mass air flow to a combustion chamber, it will satisfy combustion chamber requirements. Since it is possible to design an air driven turbine which will vary its speed against a constant torque, that is to say. vary its delivered power in direct proportion to mass air flow, such power source becomes a convenient expedient to deliver optimum amounts of fuel under the variable flight conditions mentioned. This is possible if the turbine is disposed near the mouth of a. ram jet as shown in Fig. 1. At this point the air velocity through the mouth is substantially equal to the free stream air velocity and therefore the turbine speed will be proportional to'flight velocity and it therefore follows that the pump discharge rate will be directly proportional to flight velocity. Since the mass air flow through the mouth is directly proportional to the air velocity therethrough it further follows that such velocity can be utilized as the controlling factor for maintaining a constant fuel-air ratio.

In the embodiment of the invention, as shown Fig. 1, a unitary fuel system I5 is supported within the mouth of casing Ill by webs or other structure (not shown) as will be understood to those skilled in the art. This device includes a turbine having turbine blades Ii which are driven by the air entering the engine casing. The blades, in turn, drive a fuel pump II which is supplied with fuel by a conduit l3 which is connected to a fuel tank (not shown). This fuel system replaces the system of stationary fuel nozzles, fuel pump, etc., previously referred to and constitutes the principal feature of this invention.

In greater particularity still referring to Figs. 1 and 2, turbine blades ii are fixedly mounted to one end of a hollow shaft IS. The blades of the turbine have a passageway therein which communicates with the bore of the hollow shaft and also with a series of discharge holes or orifices 2| in the rearward faces of the blades. The opposite end of shaft I3 is drivingly connected to a pump II illustrated as a vane type but which could be any other suitable type such as gear, piston, etc. Discharge of the pump is through conduit 22, valve 23, and conduit 24, thence to the bore of the hollow shaft through suitable holes therein.

The discharge holes 2| may be varied in number, size, or relative location along the length of blades It so that the amount of fuel discharged into any increment of cross sectional area of the ram jet may be chosen as desired. In many cases it will be desirable to maintain the fuel-air ratio substantially constant across the cross sectional area, however, in others it may be more desirable to vary the fuel air ratio in different regions. Either condition may be achieved by suitable design of the holes 2|. It is to be observed also, that since the discharge holes are located on the downstream or low pressure side of the turbine blades the back pressure against which the pump must operate is reduced. This is so since the turbine blades can be made as an air foil section and the holes located at a position along the length of the air foil where the air pressure is a minimum. Advantage is also taken of centrifugal force of the liquid passing through conduits 23 which further reduces the work required of the pump. The turbine blades also change the streamline flow of air into a somewhat turbulent flow and since the fuel is introduced into this turbulent flow more uniform mixing of fuel and air is achieved.

To summarize the operation of the embodiment so far described, fuel enters i8, passes through pump I1, is delivered to discharge holes 2| by conduits 2-2 and 24, hollow shaft l8 and passages 20. As the mass air flow through the ram jet varies as a result of changes of altitude and/or velocity the turbine and pump, being responsive to air mass flow, change in speed to retain the fuel-air ratio constant thus providing optimum combustion.

The foregoing relation will be true only within certain limits however, and when mass air fiow is not within these limits the pump will not deliver fuel at a constant fuel-air ratio. To overcome this difilculty in installation where the mass flow varies between limits in excess of those described, valve 23 may be employed as a control to regulate fuel flow. Thus the turbine and pump could be designed to deliver an excess of fuel under all conditions and the flow throttled by valve 23 to the optimum amount required under the variable conditions. This valve could be under manual or automatic control. In certain types of guided missiles, for example, where the velocity and altitude are determinable as a function of time, the valve could be controlled by suitable mechanism operated in response to time to regulate the position of the valve for optimum fuel flow at all points of the missile trajectory.

Fig. 3 illustrates a modification of Fig. 2, valve 23 thereof being illustrated as a valve 23 operated by an automatic controller. This controller comprises a casing 33 separated into chambers 3| and 32 by a diaphragm 33 the movement of which positions valve 23' for optimum fuel flow. Static air' pressure is applied to chamber 32 by conduit 34 which tends to close the valve. Air at ram pressure is applied to chamber 3| through conduit 35 and tends to open valve 23'. A suitable orifice 33 is provided to effect a pressure drop between ram and static pressures. As velocity of the ram jet increases, the mass air flow and ram pressure increase which increases the pressure differential across orifice 33 opening valve 23' to provide increased fuel flow required to maintain the fuel air ratio constant. If the velocity is decreased the reverse operation takes place. In order that the fuel will be properly metered under variable altitude conditions barostat 31 operates valve 38 to control the ram pressure in chamber 3|. An increase in altitude at constant velocity would call for a reduction in fuel flow. Under this condition evacuated barostat 31 would expand tending to close valve 34. This would throttle the ram pressure and reduce the pressure differential across orifice 33 which in turn would permit static pressure to move valve 23' toward its closed position thus reducing the fuel flow. While the arrangement above described would ordinarily be required in the conduit 22, 24 of Fig. 2 only when the mass flow limits varied beyond the limits at which the turbine and pump could deliver fuel in proportion to mass air fiow, it could nevertheless be incorporated in any installation where an added refinement of control is desired. Thus, it might be found more expedient, especially in expendable ram jets, to sacrifice the optimum in turbine design and compensate for the deficiencies thereof by use of the metering device of Fig. 3.

In Figs. 4 and 5 are shown another embodiment of the invention in which the turbine blades are disposed rearwardly of the mouth, that is, in the diffuser section. In this region the air velocity is less than air velocity at the casing mouth but the air density is greater due to diffusion which occurs between the casing mouth and regions rearwardly thereof. At this point the"air mass fiow will not be directly proportional to air velocity as in the embodiment of Fig. 1, the mass flow being proportional to the product of velocity and air density. It is therefore necessary-to regulate fuel flow in response to these two factors rather than velocity alone. To this end, the turbine blade roots are rotatably mounted at 43 so that their pitch may be changed. The

pitch changing mechanism includes a pressure responsive bellows 4| which is connected to the blade roots by links 4!. Expansion or contraction of the bellows will therefore rotate the blades and change the pitch thereof. The outer ends of links 42 are engaged with opposite ends of beam 45, respectively, said beam being carried by the movable portion of bellows 4|. The remaining ends of links 42 are engaged with en- R air velocity would tend to increase turbine speed but not in direct proportion to such increase if the turbine blades were of fixed pitch. The increased air density however, increases the blade pitch which also tends to increase turbine speed. The cumulative effect of both velocity and air density will therefore provide a turbine speed substantially directly proportional to mass flow as in the embodiment of Fig. 1 and hence deliver fuel at a constant fuel-air ratio. The remainder of the system to the right, that is, rearwardly of the broken line would be the same as that shown in Fig. 2 except that if desired as an added refinement, the control of Fig. 3 could be employed with the embodiment of Fig. 4.

The embodiment of Fig. 5 further differs from that of Fig. 1 in that a casing 50 is disposed within the diffuser section providing an annular channel 5|. This channel by-passes a portion of fuel-less air around the combustible mixture which passes through casing 50. As this air enters the combustion chamber it continues to follow the combustion chamber wall thus cooling same. As a result of this cooling higher temperatures and hence greater thrust may be achieved. In such installations where this cooling effect is not required casing 50 would be eliminated.

While two specific positions of the turbine blades have been disclosed, it will become apparent that any intermediate positions or a position rearwardly of that shown in Fig. 5 could be employed if desired and that regardless of such positions the turbine blades can be made to operate a fuel pump in a manner such that it will deliver optimum fuel under variable conditions of velocity and/or air density. The air duct 50, while described principally in connection with the location of the turbine blades as illustrated in Fig. 4 could be employed in the embodiment of Fig. 1. The only essential difference would be that it would be arranged with respect to the casing l0 and distribution holes 2| in a manner such that a portion of the air would be by-passed around the combustible mixture for subsequent cooling of the casing l0. Also, while the illustrated embodiments show fuel discharged downstream it could be discharged upstream if desired. Many other modifications within the spirit of the inascasie vention will occur to those skilled in the art and the specific disclosure is therefore intended to be by way of example rather than limitation except as limited by the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. In a fuel system for a ram Jet engine having a casing the combination comprising; an air driven turbine adapted to be mounted within the air stream in the casing and having a rotor provided with fuel delivery passages from its hub to nozzles on its blades, and a fuel pump driven by said turbine having a delivery into said rotor hub for supplying fuel to said engine, whereby a constant fuel-air ratio may be obtained through a wide range of air speeds and densities.

2. In a fuel system for a ram jet engine the combination comprising; an air driven turbine having blades mounted within the airstream in the engine, a sliding-vane fuel pump driven by said turbine, and fuel discharge means in said blades to which said pump supplies fuel.

3. In a fuel system for a ram jet engine the combination comprising; an air driven turbine adapted to be mounted within the engine, a sliding-vane fuel pump driven by said turbine and having a delivery variable with its speed, fuel discharge means rotatable with said turbine and to which said pump delivers fuel, and means to regulate the rate of flow of fuel to-said rotatable discharge means to obtain a constant fuel-air ratio throughout a range of air speeds.

4. The combination as defined by claim 3 wherein said means to regulate the rate of fiow comprises a throttle valve.

5. The combination as defined by claim 3 wherein said means to regulate'the rate of flow comprises a throttle valve and ram air pressure and ambient static pressure responsive means for controlling said valve.

6. The combination as defined by claim 3 whereinisaid means to regulate the rate of flow comprises a throttle valve and ram air pressure responsive means for controlling said valve.

7. The combination as defined by claim 3 wherein said means to regulate the rate of flow comprises a throttle valve and air density responsive means for controlling said valve.

8. In a fuel system for a ram jet engine, the combination comprising; an air driven turbine adapted to be mounted within the airstream of i the engine, a fuel pump driven directly by said turbine whereby to obtain a substantially constant air-fuel ratio over a wide range of speeds and air densities, the blades of said turbine having fuel distributing nozzles and supply passages thereto, and air density responsive means for changing the blade pitch of said turbine.

9. In a fuel system for a ram jet engine, a rotatable fuel distributor comprising an air driven turbine rotor having fuel jets on its blades fed through passages in said rotor and fuel supply means driven by said distributor to supply fuel to said passages at a rate proportional to the turbine speed to provide a. constant fuel-air ratio.

10. A unitary fuel supply system for ram jet engines comprising an air driven turbine having blades with passageways therein, one or more discharge orifices in a face of said blades communicating with the respective passageways, a hollow shaft to which said blades are affixed at one end thereof and connecting with said passages, pump means driven by said turbine, said pump means comprising a housing and pump vanes rotatable therein secured to the other end of said shaft, and conduit means for delivering fuel discharged by said pump to said hollow shaft.-

11. A fuel supply system for a ram jet engine comprising a streamlined body positioned in the air inlet of a ram jet engine, a rotatable shaft" journalled in said body, a passage in said shaft, an air-driven propeller fixed to said shaft, a fuel delivery passage in said propeller and delivery'i ports therealong connecting with said passage, a vane type fuel pump mounted on said shaft, and a fuel delivery conduit connecting said fuel pump with the passage in said shaft.

12. The device as described in claim 'll in which said fuel delivery conduit includes a metering means with control means responsive to ram air pressure, and a second control means for said metering means responsive to ambient atmospheric pressure,

, WALTER K. DEACON.

(References on following page) 7 REFERENCES crran The following references are of record in the file of this patent:

UNITED STATES PATENTS Numser Name Date Lewis Aug. 13, 1912 Koenlg Feb. 22, 1921 Peterson Aug. 2, 1927 Davidson July 21, 1931 Davidson Apr. 25, 1933 Stephens Feb. 28, 1939 Number Name Date Fawkes June 20, 1944 Way Aug. 13, 946 Walton Nov. 5, 1946 Dewey Mar. 28, 1950 FOREIGN PATENTS Country Date France 1- Feb. 27, 1939 Great Britain June 26 1919 Great Britain Dec. 6 1935 Great Britain Aug. 28, 1940 

